NWS Medford, OR wrote its last area forecast discussion before the first event at Sep 7, 7:55 AM PST, 4 minutes earlier.
Area forecast discussion, Sep 7, 7:55 AM PST, 4 minutes before
Area Forecast Discussion
National Weather Service Medford OR
855 AM PDT Sat Sep 7 2024
.DISCUSSION...This morning temperatures started in the 60s west
of the Cascades with 50s in the east. It will be a warm day with
highs in the 80s and 90s and 70s near the coast.
Current satellite shows more cumulus moving through the area and
radar has a few showers just clipping eastern Lake County that are
moving north. Latest model runs have shown a more southward trend to
the shower/thunderstorm chances this afternoon. Heading into next
week the next trough that moves in that will bring cooler
temperatures and some rain, although there are differences in where
the low will move and in turn how much rain is expected. This will
be the main area of focus for the afternoon update.
&&
.MARINE...Updated 845 AM Saturday, September 7, 2024...Moderate
north winds will continue steep seas in the outer waters, beyond 10
nm, into this evening. Steep seas could also briefly reach the inner
waters. Winds will decrease and seas will subside tonight into early
Monday. A brief increase in wind dominated seas is likely on Monday,
with low end Small Craft conditions possible for the outer southern
waters. Weak low pressure will move into the waters Tuesday with
light to moderate winds. Some evidence points towards increasing
north winds later next week. _petrucelli
&&
.FIRE WEATHER...Issued 800 AM Saturday, September 7, 2024...Hot, dry,
and unstable conditions will continue into this weekend. Isolated
dry thunderstorms remain a concern for today. Additionally, gusty
winds and low humidities may result in brief or local critical
conditions for areas in the Scott and Shasta Valleys and east of the
Cascades.
Current models show the upper level disturbance remaining just off
the southwest Oregon coast today, then gradually moving inland
tonight and east on Sunday. This slightly slower inland progression
is allowing for isolated showers and thunderstorms to develop over
eastern portions of the area, including Lake and northern Klamath
Counties. This is also a very low (10%) chance for storms into
eastern Douglas County this afternoon/evening. We have updated the
forecast to reflect this changes and added a headline. Storms
are expect to be isolated and have some rain with them. Gusty
outflows are possible again near thunderstorms.
Gusty south to southwest winds and dry humidities are expected again
this afternoon and early evening, for the Scott and Shasta Valleys
as well as for some areas east of the Cascades into southeastern
fire weather zone 624, southern 625 and eastern 285. Conditions may
near critical RH/wind levels in these areas. A headline is in the
forecast for these potential conditions.
Sunday and Monday, temperatures are expected to trend less warm as
another upper trough approaches the region. However, humidities will
remain dry. On Monday, there is also a potential for some breezy
afternoon conditions in Modoc and Lake counties. The trough and
associated front will then move through Tuesday and Wednesday,
resulting in chances for light rain showers and isolated
thunderstorms, cooler temperatures, and a potential for breezy to
gusty winds. Confidence is low on the strength of this trough and
how much rain will arrive, but there is a chance (10-20%) for
wetting rainfall (0.25"+) on Wednesday for areas from the Cascades
west. The thunderstorm potential is current low (10-20%) and is
focused on Wednesday for areas east of the Cascades, mainly in Lake
and Modoc counties.
-CC
&&
.PREV DISCUSSION... /Issued 448 AM PDT Sat Sep 7 2024/
Updated Aviation Discussion.
DISCUSSION (Today through Friday)...
Overview:
With this round of thunderstorms in the rearview mirror, we are now
focused on the trend towards cooler temperatures next week, and a
chance at widepsread light rainfall during the middle of next week
(Tue/Wed). That being said, we are still going to see at least
elevated/near-critical fire weather candidness through the weekend
and into Monday given the hot, dry, and at times breezy conditions.
Please see the fire weather section below for further information.
Further Details:
Upper level shortwave trough will continue to pass through the
region today, yet the placement/orientation of the upper level
energy should keep most of the convection north and east of our
forecast area. However, there is an area of potential development
across northern portions of both Klamath and Lake Counties where
lingering PVA continues to round the trough. We can see this now on
radar with some high based cells over northern Lake County. Very
little--if any--rainfall is actually hitting the ground given the
dry air near the surface. This leads to the potential for virga to
create some gusty winds now through late morning/early afternoon. We
could see gusty winds around 25-45 mph through this timeframe. Dry
air is anticipated to move in quickly this afternoon, so can't image
these chances going too far into the afternoon as showers run out of
moisture for development. This chance is <15% given the progression
of the disturbance, but if the trough happens to slow down at all we
could see those chances increase. Something to watch for later to
update the forecast as needed.
We will end the weekend and go into early next week under zonal flow
as the aforementioned trough slides east. By Tuesday, we will see
the early stages of a developing trough over eastern parts of the
Gulf of Alaska. This trough will dig south and eventually a broad
area of cyclonic flow will consume the western CONUS. Deterministic
models are in generally good agreement through Wednesday evening
which does boost confidence for this rainfall event. However, there
are some stark differences within the suite of ensemble members,
especially the suite of GFS ensemble members versus the EC members.
Of the 30 members from the GFS, only a handful have QPF compared to
the EC where nearly every member (out of 50) has QPF. This is really
concerning with regards to confidence in the forecast. Interestingly
enough, the National Blend of Models (NBM) has increased the
probability for 0.10" or more of rainfall over 48 hours ending
Wednesday night/Thursday morning. That probability is now 30%-60%
for 0.10" or more of rainfall compared to 24 hours ago when it was
10%-40%. The NBM does weigh the EC more in the extended so its not
completely a shock, but this is something we should watch going
forward because at this time widespread light rainfall does appear
to be a possibility. We will continue to monitor this next system as
the rainfall would be welcoming to the wildfire situation across the
region.
Lastly, we are looking at a significant cool down next week compared
to the last couple of days. Wednesday will be the peak of this
cooling with high temperatures likely not hitting 80 degrees for
nearly the entire area. The probability for 80 degree high
temperatures or greater on Wednesday is 0-10%. On Thursday, even our
hotter locations (valleys) only have a 20-30 percent chance of
hitting 80 degrees. So, we are looking at the potential for highs to
be about 25+ degrees cooler than the last couple of days. Its going
to actually feel like fall middle of next week with cooler temps,
clouds, and light rainfall.
-Guerrero
AVIATION...07/12Z TAFS...Along the coast and over the marine
waters, stratus and fog will result in continued IFR/LIFR ceilings
for all areas, including North Bend for most of the TAF period. It's
possible ceilings could briefly improve to MVFR between 21-23z, but
confidence is high enough to include this at the North Bend TAF.
The marine stratus will push into the lower Umpqua and Coquille
valleys by daybreak, but will stay north and west of Roseburg, then
burn off between 16-18z. Marine stratus will return in similar
locations late tonight.
Elsewhere VFR conditions will continue through the TAF period. The
exception will be in the vicinity of the Devils Knob Fire and areas
to the north where MVFR visibilities are possible. -Petrucelli
&&
.MFR WATCHES/WARNINGS/ADVISORIES...
OR...None.
CA...None.
PACIFIC COASTAL WATERS...Small Craft Advisory until 8 PM PDT this
evening for PZZ370-376.
&&